Hydrofoil craft



Sept. 19, -1967 c. HooK HYDROFOIL CRAFT Original Filed June 7, 1965 5 Sheets-Sheet l Sept. 19, `1967 c. HOOK HYDROFQIL CRAFT 5 Sheets-Sheet 2 Original Filed June 7, 1965 im 5 M i P N i un u WH C 5 Sept. 19, 1967 Q HQOK 3,342,155

HYDROFOIL CRAFT United States Patent O No. 589,766 Claims priority, application Great Britain, June 11, 1964, 24,231/64; July 8., 1964, 28,046/64 Claims. (Cl. 114-665) This application is a division of my ycopending application Serial No. 461,777, liled June 7, 1965, and entitled Hydrofoil Craft.

This invention relates to hydrofoil craft and more particularly to such craft that use fully submerged foils wherein the lift is varied by changing the angle of incidence (attack) of the foil relative to the water ilow or line of flight.

Hydrofoil craft which travel over the water on hydrofoils connected to the hull by vertical struts are more vulnerable to floating `debris such as logs of Wood than are normal boats, and it is important to provide means whereby such floating debris cannot endanger the safety of the craft or passengers or cause any serious material damage.

With the fully submerged type of foil this danger is somewhat greater, and the need for foil safe provisions therefore more apparent. The reasons are basically:

(l) Not having emerging foil tips that can 4be set at a larger angle of attack (as in those hydrofoil craft which use the emerging foil area method of control in altitude) there is nothing to stop a bad crash when air enters the low pressure area above the foil and the lift is lost.

(2) In order to make air entry to the foils more diliicult these are mounted at the bottom but to the front of the vertical struts attached to the hull. In this position they tend to hook on to any log of wood or other similar obstruction and its liberation is more difficult.

The invention accordingly consists in a variable-incidence hydrofoil assembly for a hydrofoil craft comprising a strut adapted to be attached to a hull of the craft for pivotal movement about an athwartships axis, means adapted to locate the strut in a generally vertical position and yieldably to restrain it from movement from that position, a hydrofoil pivotally mounted on the strut about an athwartships axis, a control rod passing down the strut, and means connecting the hydrofoil to the control rod `to vary the angular location thereof in relation to the strut and for releasing the hydrofoil from the control rod when the angle of incidence assumes an effective negative value beyond a predetermined limit.

Preferably, the connecting and releasing means comprises gearing over a limited arc whereby the hydrofoil `can be released from the control rod on movement outside the range covered by the arc.

Thus, on hitting a log or similar heavy object in the water the strut shall first swing rearwards through a small angle and from the athwartships pivot located near the top of the strut. The strut is normally held in an upright position by the said pivot together with another member or strut attached to a point below the pivot and going rearwar-ds to a point on the hull. This member can conveniently be a hydraulic piston or actuator which, on extension retracts the whole strut forward and upwards so that the foil comes ont of the water. Rearwards of the upright position the strut will incline backwards so that the log tends to be pushed downwards and the hull to ride over the log. At this point a downward pressure will be exerted on the foil both by the log and by the water and when this force has reached a predetermined value the foil will assume the negative incidence and the whole foil shall turn over about its pivoted mounting thus allowing the log to pass and the strut to ride up over it.

Over the normal working range of incidences necessary -to fly the boat the teeth will mesh, but when on swinging back the log forces the foil to a much more negative angle than that required for flight the two gears will no longer be meshed together but will be free so that the vfoil can turn right over. This is accomplished by ending the yteeth at that position and indeed only a small sector of teeth is required.

In order that this free sector shall not be used in normal flight, in which case the boat could turn over for lack of proper incidence control, it is best protected by suitable shear pin devices. Likewise the strut cannot depart from its normal upright position and incline rear- Wards before a shear pin has been `broken by the exceptional drag given by the log.

The method has the advantage over other systems wherein the foil is attached by shear points to the hull that with this means the foil is not lost and can be brought back into mesh with the teeth after the strut has been retracted.

The invention further consists in a hydrofoil craft having a pair of hydrofoil assemblies according to the invention as set forth above mounted on the hull thereof.

The manufacture of large highly stressed hydrofoils in steel has presented hitherto almost insurmountable problems of manufacture.

The main difficulty is that the foil must have an ankle joint at or near its hydrodynamic centre if difficult forces are to be eliminated from the controls. It follows that for such a joint to be clean and well streamlined to avoid corrosion-producing cavitation at high speeds it must be well blended into the depth of the foil thickness and the corresponding or mating strut joint has similar very diflicult requirements. Normally the centre of pressure of a foil falls at or very near the 25% chord point but in view of the angle of sweep it falls at about of the chord on the centre line where the foil starts to become thin. However, another requirement of cavitation avoidance requires the presence of a body of revolution along the centre line with the nose -a short distance in advance of the apex of the two wings. It is inside this body that the hinge can be merged by blending the circular nose shape progressively to a square shape in the region of the pivot. However if the body has to be cast together with the foil there is no Way of turning it on a lathe and machining the surfaces of the joint is made almost impossible in view of its difficult location.

In a second aspect the invention accordingly consists in ya variable-incidence hydrofoil for a hydrofoil craft, comprising a hydrodynamically` streamlined central section generally in the form of a body of revolution, said central section at a rear portion thereof for pivoting the hydrofoil to a supporting strut and a recess therein, and a hydrofoil section having a projection entering the recess, the hydrofoil section and the central section being secured together.

The invention further consists in a hydrofoil assembly including such a foil, and in a hydrofoil craft having a pair of such assemblies.

The problems of safe failure for a hydrofoil drive mechanism of the two drive form is somewhat more complex than the corresponding problem for the variable incidence hydrofoils, because of the need to cater for the transmission of drive, for steering, for the retraction of the drive, and possibly for incidence variation on the tail foil.

In those struts which are used to transmit power to a propeller, generally known as Z-drives, it has been customary to exploit the special qualities of the Cardan joint to both eliminate the torque reaction of the propeller from the steering gear and to allow fail safe and retraction. However all previous systems have certain limitations and some sacrifice both the Cardan and the tail foil when the fail safe is used. This represents a grave breakdown which in the ocean might be dangerous.

Two known types of hydrofoil craft have different advantages and drawbacks. One offers incidence correction to the tail foil by adjustment of the strut out of the vertical, but destroys its drive Cardan joint on fail safe and does not retract the foil clear of the water. The other retracts its foil completely but lacks fail safe.

It is a further object of the invention to provide a system in which all these requirements are met.

Accordingly in a third aspect, the invention consists in a drive and tail foil assembly for a hydrofoil craft, comprising a main strut having a hydrofoil and a propeller mounted thereon and carrying an outboard drive mechanism for the said propeller, a secondary column including pintles rotatably supporting the main strut about a steering axis, an inboard drive shaft being driveably coupled to the outboard drive mechanism by a universal joint located on the said steering axis, the said secondary column being pivotally mounted in a bracket, about a fail safe pivot axis, the fail safe pivot axis being generally horizontal during flight of the craft, yieldable means restraining the secondary column from pivoting about the said fail safe pivot axis, the said bracket being pivotal about the axis of the inboard drive shaft to retract the assembly so that the foil and propeller are out of the water, and releasable means for holding the said assembly in operation position to prevent retraction.

The invention further consists in a hydrofoil craft including such a drive and tail foil assembly.

The invention will be further described with reference to the accompanying drawings wherein:

FIGURE 1 is a side elevation of a preferred form of hydrofoil craft according to the invention;

FIGURE 2 is a side elevation showing the fail safe action of a variable incidence foil;

FIGURE 3 is a side elevation of a hydrofoil;

FIGURE 4 is a plan View, partly in horizontal section, of the foil of FIGURE 3;

FIGURE 5 is a section on the line V--V of FIGURE 4; and

FIGURE 6 is .a section through the upper part of a drive and tail foil assembly in position at the stern of the craft.

FIGURE 1 shows a hydrofoil craft having a hull 1. Forward, variable incidence hydrofoils 2 are pivoted in vertical struts 3. The struts are pivotal about an athwartships axis 4 and are yieldably located in the normal vertical position by a hydraulic piston cylinder unit 5 pivoted to the hull 1 and the strut 3. In addition a shear pin (not shown) may be incorporated to avoid the need for critical loading of the unit 5.

At the stern the craft has a further single vertical strut 7 housing a drive from an inboard motor to a propeller 8. The strut 7 also supports a fixed hydrofoil 9.

FIGURE 2 shows diagrammatically what happens when one of the variable incidence hydrofoils 2 strikes a floating obstruction such as a log 10.

It will be understood that in the majority of cases the obstruction will be swept out of the way or broken or cut by the impact, but occasionally a bulky obstruction will get caught on the strut. In order to protect the strut and hydrofoil from damage, which could incapacitate the craft, the strut 3 is so mounted, as described above, that it will yield under a predetermined stress and pivot to the position shown dotted. The change of angle might be suicient to dislodge the obstruction, but if not the foil itself is also so mounted as to retract to the position shown dotted, to allow the obstruction to pass under the foil, upon being stressed above a predetermined limit. The manner in which this is achieved will be described with reference to FIG- URES 3 to 5. It will be appreciated that such a movement of the foil will cause the craft to settle violently into the displacement mode of operation, but this is acceptable in View of the rarity of the occurrence. After resetting, however, the craft may normally recommence flight on the hydrofoils.

As shown in FIGURES 3 to 5, the hydrofoil 2 has a centre section 11 of rectangular form which merges into a tapered section 12 at the bottom of the strut 3. The section 12 includes a pair of forwardly extending ears 13 and the rear portion 14 of section 12 is interdigitated with the ears 13. A stressed pivot pin 15 is inserted through the ears 13 and interdigitated rear portion 14.

A gear tooth section 16 is securely welded to the centre rear portion 14, and meshes with a sector 17 on a link 18 mounted on a pivot pin 19 in the tapered section 12. The link 18 is pivoted to a centr-al rod 21 which extends through the strut and is hydraulically actuated from within the craft to control the angle of incidence of the foil in response to pilot operated and automatic, wave-compensating controls.

The rear teeth 17 preferably form a pinion so as to give a mechanical advantage and reduce the force necessary to move the foil by the control rod.

The normal extreme positions of the link 18 are shown dotted in FIGURE 5. Upon the hydraulic control, and possibly a shear pin device, being overcome by an excessive stress due to an obstruction so as to cause negative incidence of the foil above that indicated by the angle 0 the teeth 16 and 17 are released and the foil is free to retract to the position shown dotted in FIGURE 2 to allow the obstruction to pass clear.

In order to simplify the manufacture of the hydrofoil, the central portion 31 is made separately, generally in the form of a body of revolution -of hydrodynamically streamlined form, which form is continued by the profile of the adjacent part of strut as seen in FIGURE 4. A recess 32 is machined in the underside of the portion 31. The hydrofoil itself is formed with a machined projection or flat 33 matching the recess 32.

This enables the cross sectional area of the foil at the centre, its highest bending moment position, to be almost as large as the cross sectional area of the foil shape immediately adjacent to the centre portion 31 and the foil can be cast in a single piece with full strength. The final joint of foil to body of revolution may be by welding or other fastening method. The foil being underneath, the lift tends to close the joint.

FIGURE 6 shows in section the upper part of the strut 7 of FIGURE 1 and the details of its attachment to the hull 1.

The strut 7 carries a final drive shaft (not shown) to the propeller 8, which final drive shaft is connected to a vertical intermediate drive shaft 41. A horizontal outboard drive shaft 42 has bevel gears 43 and 44 rotatably mounted thereon and selectably connectable thereto by dog clutch shift sleeve 45. The bevel gears 43 and 44 are in mesh with a bevel gear 46 solid with shaft 41, to provide forward and reverse drive.

An inboard drive shaft 47 is drivably connected to an engine and transmission (not shown) and also to the outboard drive shaft 42 by means of a universal 'joint 4S. The axes of the shaftsv 42 and 47 meet at a point 49.

A secondary column S0, parallel with the strut 7 is provided with upper and lower pintles 51 and 52 defining a steering axis 53 passing through the point 49. Upper and lower arms 54 ,and 55 support the strut 7 steerably on the pintles. The actual steering mechanism is conventional and is not shown. The column 50 is pivoted about an athwartships fail safe axis passing through the point 49 to a bracket 56.

The lower pintle 52 has a downward extension terminating in a head 57 provided with a steeply inclined yramp surface 58 at its rear side. The head is received in a cooperating recess 59, having an inclined surface 60` adjacent t-he surface 58, in a bracket portion 61. Together with a main body portion 62, to which it is secured by a shear pin 63, the portion 61 forms a releasable L-shaped bracket. To provide release, the portion 62 is mounted in a lathe-saddle type of slide for vertical movement in a thrust block 64. Mechanism, not shown, is provided for moving the portion 62 downwards from and upwards to the position shown in FIGURE 6 to release and secure the secondary column 50, and hence the whole final drive and tail foil assembly.

The thrust block 64 is itself mounted in a lathe-saddle type of slide in a block 65 securely attached to the hull 1. A cam 66 on a camshaft `67 passing through the hull co-operates with a recess in the block 64 to provide fore and aft movement from the position illustrated in order to move the pintle 52 forward and aft to vary the incidence of the tail foil, for purposes of takeoff. The camshaft has a crank 68`thereon which is `attached to a control mechanism under the pilots control.

The bracket 56 consists basically of a plate 71 parallel with the transom and of generally annular shape with a central aperture for the shaft 47 to pass through. An outer peripheral flange 72 is provided with gear teeth (not shown) for co-operation with a pinion (not shown) to rotate the bracket. The secondary column 50 is supported between two ears merging with the flange 72. A rubber or elastomer cushion block 73 is mounted on the plate 71 to limit movement of the column Si) about the fail safe axis.

The shaft 47 passes through an aperture in the transom and a sleeve 74, provided with supporting plates 75 and 76 is securely mounted in the transom so as to line and extend the aperture. A sleeve 77 is welded by its flange 78 into the aperture in the plate 71. This sleeve 77 is coaxial with the sleeve 74 and is rotatable thereon, being normally restrained against rotation by a removable pin 79. The shaft 47 is supported in the sleeve 77 by bearings 81 and 82 and seals 83- and 84 are retained by collars 85 and 86.

When retraction of the drive and tail foil assembly is required the body portion `62 and portion 61 are lowered in the slide block and the pin 79 is removed. rl'he bracket 56 and drive assembly can`then be rotated about the axis of the shaft 47 using the pinion and tooth arrangement described. To provide stability in the retracted position, a coupling (not shown) may be provided to secure the end of the column 50 carrying the pintle 52 to the transom. The reverse procedure secures the assembly in normal operating position as illustrated.

On takeoff `the block 64 is normally moved forward to increase the angle of incidence of the tail foil and is brought back to its normal position as illustrated once flight and speed have been established.

Normal drive thrust to the craft for the propeller is a forward thrust taken through the head 57 on the pintle 52 and transmitted through the thrust block 64. When the strut 7 strikes a floating obstruction, the obstruction is normally cut through or diverted without trouble. However Ioccasionarry a reverse thrust is applied to the strut 7 and this is applied by the lower arm 55 to the pintle 52. This causes the inclined surfaces 58 and 60 to engage and thus a downward thrust is exerted on the releasable bracket formed by portions 61 and 62 to overcome the restraining means holding the bracket in position. This bracket then drops to release the pintle and allow the assembly to pivot about the fail safe axis through about 45 until the upper end of column 50 strikes the cushion 73. In the alternative, the shear pin 63 will fail and release lower end of column 50. In this case the bracket portion 61 will be lost and must be replaced before the voyage can be continued.

A trigger is also provided to cut out the engine as soon as the load is shed by fail safe mechanism as described. This may conveniently be operated by any part that moves on fail safe coming into operation.

An advantage of the use of a horizontal slide for the block 64 is that it enables the thrust from the propeller, augmented by the mechanical advantages due to the lengths involved, to be measured for the purposes of research.

Various modifications may be made within the scope of the invention.

I claim:

1. A drive and tail foil assembly for a hydrofoil craft, comprising a main strut having a hydrofoil and a propeller mounted thereon and carrying an outboard drive mechanism for the said propeller, a secondary column including pintles rotatably supporting the main strut about a steering axis, an inboard drive shaft being driveably coupled to the outboard drive mechanism by a universal joint located on the said steering axis, the said secondary column being pivotally mounted in a bracket about a fail safe pivot axis, and fail safe pivot axis being generally horizontal during flight of the craft, yieldable means restraining the secondary column from pivoting about the said fail safe pivot axis, the said bracket being pivotal about the axis of the inboard drive shaft to retract the assembly so that the foil and propeller are out of the water, and releasable means for holding the said assembly in operation position to prevent retraction.

2. An assembly as claimed in claim 1, wherein the lower end of the secondary column is mounted in a releasable bracket adapted to be moved downwardly to release the assembly for retraction, the said bracket constituting the releasable restraining means.

3. An assembly as claimed in claim 2, in which the releasable bracket is slidably mounted in a thrust block secured to the hull of the craft.

4. An assembly as claimed in claim 3, in which the longitudinal position of the thrust block on the craft is variable to provide for incidence variation in the tail foil.

`5. An assembly as claimed in claim 4, in which the thrust block is mounted in a slide block in which its position is determined by the angular position of a cam on a camshaft passing through the hull. i

6. An assembly as claimed in claim 2, in which the lower end of the secondary column is mounted in a part of the releasable bracket secured to the main body by a sheer pin device adapted to fail on excessive reverse thrust being 'applied to the tail foil assembly, such as might be caused by striking a floating obstruction.

7. An assembly as claimed in claim 2, in which the lower end of the secondary column is supported in the releasable bracket by an element having a steeply inclined ramp co-operably engageable with a corresponding ramp in a recess of the releasable bracket whereby reverse thrust has a tendency to urge the releasable bracket downwardly to release the secondary column and 4allow it to pivot about the fail safe pivot axis.

8. An assembly asrclaimed in claim 1, in which the bracket pivotable about the axis of the inboard shaft comprises peripheral teeth engageable with a pinion to rotate the said bracket.

9. An assembly as claimed in claim 1, in which the fail safe pivot axis passes through the universal joint.

10. A hydrofoil craft including a hull having a drive and tail foil 'assembly attached thereto, the said assembly comprising a main-strut having a hydrofoil and a propeller mounted thereon and carrying an outboard drive mechanism for the said propeller, a secondary column including pintles rotatably supporting the main strut about a steering axis, an inboard drive shaft being driveably coupled to the outboard drive mechanism by a universal joint located on the said steering axis, the said secondary column being pivotally mounted in a bracket about a fail safe pivot axis, and fail safe pivot axis being generally horizontal during flight of the craft, yieldable means restraining the secondary column from pivoting about the said fail safe pivot axis, the said bracket being pivotal about the axis of the inboard drive shaft to retract the assembly so that the foil and propeller are out of the water, and releasable means for holding the saidwassembly in operation position to prevent retraction.

References Cited UNITED STATES PATENTS 3,136,286 6/1964 Kiekhaefer et al 11S-41 MILTON BUCHLER, Primary Examiner.

A. H. FARRELL, Examiner. 

1. A DRIVE AND TAIL FOIL ASSEMBLY FOR A HYDROFOIL CRAFT, COMPRISING A MAIN STRUT HAVING A HYDROFOIL AND A PROPELLER MOUNTED THEREON AND CARRYING AN OUTBOARD DRIVE MECHANISM FOR THE SAID PROPELLER, A SECONDARY COLUMN INCLUDING PINTLES ROTATABLY SUPPORTING THE MAIN STRUT ABOUT A STEERING AXIS, AN INBOARD DRIVE SHAFT BEING DRIVEABLY COUPLED TO THE OUTBOARD DRIVE MECHANISM BY A UNIVERSAL JOINT LOCATED ON THE SAID STEERING AXIS, THE SAID SECONDARY COLUMN BEING PIVOTALLY MOUNTED IN A BRACKET ABOUT A FAIL SAFE PIVOT AXIS, AND FAIL SAFE PIVOT AXIS BEING GENERALLY HORIZONTAL DURING FLIGHT OF THE CRAFT, YIELDABLE MEANS RESTRAINING THE SECONDARY COLUMN FROM PIVOTING ABOUT THE SAID FAIL SAFE PIVOT AXIS, THE SAID BRACKET BEING PIVOTAL ABOUT THE AXIS OF THE INBOARD DRIVE SHAFT TO RETRACT THE ASSEMBLY SO THAT THE FOIL AND PROPELLER ARE OUT OF THE WATER, AND RELEASABLE MEANS FOR HOLDING THE SAID ASSEMBLY IN OPERATION POSITION TO PREVENT RETRACTION. 